1. Field of the Invention
The invention concerns the field of lighting devices, and more particularly the field of car headlamps comprising one or more optical modules, each optical module comprising at least one light source associated with optical elements in order to emit one or more types of light beams. The invention relates to a headlamp comprising at least one optical module, which is capable of selectively lighting a zone by means of a cut-off member of a light beam emitted by the module. The headlamp of the present invention is more particularly capable of optimizing the lighting of a zone excluding a changing space in which there is located a travelling vehicle whose driver must not be dazzled.
2. Description of the Related Art
Headlamps for a motor vehicle are generally composed of a housing which is closed by a transparent lens through which one or more light beams are emitted. This housing accommodates at least one lighting module, comprising principally a light source and an optical system capable of modifying at least one parameter of the light generated by the light source for emission of the light beam by the lighting module. The optical system comprises optical components consisting for example of a reflector, a lens, a diffusive element or a collimator, or any other optical component capable of modifying at least one of the parameters of the light generated by the light source, such as its average reflection and/or its direction. The lighting module or modules are likely to be jointly accommodated within the same optical module or to be distributed in headlamps/optical devices specifically dedicated thereto.
Known examples of optical modules for a car headlamp include “bifunctional” modules which are configured to emit from the same lighting module alternately two types of light beams in accordance with the required lighting conditions. One of these light beams is, for example, a, short-range, low beam for lighting the lane while avoiding dazzling another driver driving in a lane in the opposite direction of traffic or in a lane in the same direction of traffic, in the case of a vehicle being tailed or during overtaking for example. The other of the light beams is, for example, a long-range, high beam allowing optimization of the lighting provided by the headlamp if there is no driver who must not be dazzled. In order to switch from low beam to high beam and vice versa, the optical module is equipped with a cover plate, which is mounted so as to be able to move within the housing of the optical module, by being in particular interposed between the light source and a component of the optical system, such as a lens or the like. This movable cover plate is a beam cut-off cover plate which allows the low beam to be emitted based on a partial masking of the light beam emitted by the optical module, which would otherwise spread above the cut-off formed by the movable cover plate. Another known auxiliary function consists in a raising of the low beam, for emission of a motorway beam of intermediate range between that of the low beam and that of the high beam.
According to a simple embodiment, the movability of the cover plate makes it possible to pass between two positions, one for partially blocking the light beam emitted by the optical module in order to obtain the low beam, the other a retracted position in which the light beam emitted by the optical module is not masked in order to obtain the high beam. There have also been proposed more complex embodiments of the movable cover plate allowing various phases for blocking of the light beam emitted by the optical module. More particularly, the blocking or non-blocking of the light beam may be carried out gradually in various successive steps. The movable cover plate is for example embodied as a rotating arbor, the outer surface of which is in the form of an envelope having a continuous surface. Reference may be made for example to document EP-0 935 728 for this type of cover plate.
A drawback of this type of movable cover plate formed by an arbor having variable geometry consists in the complexity of its structure and its means for rotating. The precision imposed by the variation in the geometry of the drum makes it expensive to produce; this is undesirable. An additional constraint consists in the need for the default position of the movable cover plate to correspond to that of the low beam, resulting in a configuration of the movable cover plate and its movability means that must make allowance for this constraint. The mounting of the rotating arbor within the housing and repositioning thereof relative to the optical axes of the lighting module must be stringent, resulting in an increase in the complexity of the lighting module. As a result, the general embodiment and the modes of operation of a movable cover plate of this type, providing various phases for blocking the light beam emitted by an optical module between the emission of a low beam and the emission of a high beam, or even of a motorway beam, are capable of further improvement.
It is known to operate means for detecting the environment of a vehicle in order to automatically vary the light beams emitted by the optical modules fitted to the headlamp. Detection means of this type allow in particular the movable cover plate of a bifunctional optical module to be automatically maneuvered for emission of the low beam or the high beam in accordance with the traffic conditions, and in particular in the case of the presence of another vehicle whose driver must not be dazzled. The detection means are in particular of the optoelectronic type, such as a camera or similar equipment, and/or of the type for communicating by waves, such as satellite and/or cellular communication means, or else of the radar type. Various computation means can be associated with the detection means in order to correct the information which they provide and complete the information detected from the environment of the vehicle.
It is also known to improve night-sight driver comfort by adapting as required the range and/or the intensity of passing beams or high beams in order to optimize the potential lighting of the traffic lane. For example, there have been proposed what is known as a motorway light function and what is known as a town light function. These functions consist in modifying the range and/or the current light intensity of the passing beams, in accordance with the traffic lane in which the vehicle is driving and/or in accordance with the conditions for lighting the external environment of the vehicle. More particularly, when a vehicle is driving in a fast-moving lane, such as a motorway or similar traffic lane, it is expedient to increase the range of the passing beams, in order to make the emitted light beam carry effectively as far as possible (motorway light function). Conversely, it is expedient to reduce the range slightly and to widen the beams emitted by the passing beams when the vehicle is driving close to an externally lit environment, such as in an urban area for example (town light function). Reference may be made for example to patent EP-1 923 262, which is equivalent to U.S. 2008/0117642, which discloses embodiments for adapting the range of a beam emitted by a low beam.
Other functions have been proposed to modify the characteristics of a light beam emitted by an optical module in accordance with the configuration of the traffic lane. Known, for example, is the “bending light” (BL) function which can be broken down into what is known as a dynamic bending light (DBL) function and what is known as a fixed bending light (FBL) function. The bending light function allows the orientation of a light beam to be modified, in the case of DBL, or light to be added laterally by switching on one or more additional light sources in bends, in the case of FBL, in such a way that when the vehicle enters a bend, the road is better lit.
However, the optimization of the lighting provided by vehicle headlamps is limited by the various regulations relating to the driving of vehicles on public roads, in particular with regard to the ban on dazzling other users of car traffic lanes, regardless of whether they are driving in a lane in the opposite direction of traffic or in a lane in the same direction of traffic. Accordingly, designers in the field focus their efforts on research into lighting devices for a motor vehicle that offer a compromise between improved lighting for the driver, with better visual comfort, while at the same time not causing any inconvenience to other road users. It has for example been suggested, in patent application DE-102006043281, to use a movable cover plate of the type of that described in patent application EP-0 935 728 in order to obtain such a result by defining various beam cut-off zones obtained from the rotating arbor having variable geometry.
There is, therefore, a need to provide an optical module that provides improved lighting over the systems of the past.